The invention relates to a method for ascending along a main rope, making use of a dynamic sit-stand system comprising a first ascender fixed to the roping harness of the climber with passage of the rope, and a second ascender joined by a link cord to a leg loop, said second ascender being engaged on the main rope above the first ascender, and the ascending movement being performed in a succession of elementary steps, each of which is generated in the course of:
a first stage involving a push on the leg loop causing jamming of the second ascender at a predetermined point of the rope, and a sliding movement of the first ascender along the rope in the direction of the second ascender, releasing the push on the leg loop in the standing position of the climber then resulting in automatic jamming of the first ascender due to the action of the climber's weight, PA1 and a second stage involving lifting of the second ascender by the climber's hand pulling the leg loop upwards to a sitting position. PA1 a first stage involving pulling on the arms and simultaneous pushing on the leg loop 16, in the course of which a vertical force F1, directed in the downwards direction D, causes jamming of the second ascender 14 by the reaction of the cord 22. The second ascender 14 remains immobilized at the point A of the main rope 10, and the first ascender 12 is urged slidingly in the upwards direction M, until the distance d is taken up by coming into abutment against the fixed second ascender 14. The leg is then stretched, and the climber is in the standing position in which, after the push on the leg loop 16 has been released, the first ascender 12 is automatically jammed by the weight P of the climber 20. PA1 and a second stage involving lifting of the second ascender 14 by the hand 24 of the climber 20 which causes the leg loop 16 to be pulled up to a sitting position, in which the leg or legs of the climber 20 are bent. PA1 a first ascender fixed to the roping harness of the climber, PA1 a second ascender engaged on the main rope above the first ascender, and able to be moved in the ascending direction by the hand of the climber, PA1 and a leg loop in the form of a pedal, cooperating with a cord one end of which is attached to the first ascender after passing over a first pulley secured to the second ascender.
There are several methods of ascending along a rope, used in caving for ascending shafts of different heights. Two of these prior art methods are described to serve as examples.
In FIGS. 1 and 2, the FROG or DED process for ascending along a fixed rope 10 makes use of a dynamic sit-stand system operating with a pair of ascenders 12,14 and a leg loop 16 in the form of a pedal. The first ascender 12 is fixed to the roping harness 18 of the climber 20, and cooperates in the ventral zone with the rope 10 to freely authorize an ascending movement of the climber 20 according to the arrow M, and to oppose any opposing descending movement D by a self-jamming action on the rope 10.
The second ascender 14 has a similar operation to the first, and is joined to the leg loop 16 by a link cord 22 having a diameter generally smaller than that of the main rope 10. The second ascender 14 is engaged on the rope 10 above the first ascender 12, and can be moved in the upwards direction M by a lifting action by means of the hand 24 of the climber 20.
The leg loop 16 is designed for placing the foot of the right or left leg or both feet in the same loop, but it is also possible to provide a pair of separate pedals for engagement of both feet of the climber 20.
The ascending movement along the rope 10 is performed in a succession of elementary steps, each of which comprises:
He then merely has to push on his legs again to come back to the standing position, and so on.
In the FROG ascending process, to ascend a step d requires a vertical movement of the same length of the second ascender 14, and of the leg loop 16. In the course of this movement, the thrusting force F1 on the leg loop 16 is appreciably equal to the weight P of the climber 20, ignoring the traction forces of the hand 24.
The FROG ascension consisting in standing (legs stretched), then sitting (legs bent), requires forces proportional to the weight P of the climber 20.
To gear down the thrusting force on the leg loop 16, the "Italian" method, represented in FIGS. 3 and 4, consists in attaching the cord 22 to the first ascender 12, with an intermediate passage over a first pulley 26 secured to the second ascender 14. The link cord 22 forms a half-turn mounted on the pulley 26, and connected respectively by its opposite ends to the first ascender 12 and to the leg loop 16.
The gearing down effect generated by the presence of the pulley 26 enables the effort exerted on the leg loop 16 to be divided by two in comparison with the FROG process. The force modulus F2 (FIG. 4) corresponds appreciably to half of the weight P of the climber 20, naturally ignoring the traction forces of the hand 24. But the shortcoming of this "Italian" method lies in the greater movement of the leg loop 16.
For the climber 20 to ascend one step along the rope 10, the vertical movement of the leg corresponds appreciably to a doubling of the distance of the step. This results in a certain slowness of movement, and this method is not suitable for ascending shafts of large heights, for example more than 15 meters, because of the breathlessness it causes.
A first object of the invention consists in finding an efficient method for ascending along a rope, whereby the problems of gearing down efforts can be conciliated with the movement travel.